A conventional probe apparatus for testing semiconductor devices includes a number of interconnect structures for temporarily contacting test terminals of the tested device. As the semiconductor technology advances, the tested devices become increasingly smaller while the number of simultaneously accessed terminals continues to increase. At the same time, commercial competition forces the industry to provide semiconductor testing at ever decreasing cost. To meet these demands, there exists a need for further improvement of probe apparatus.
A crucial component in a probe apparatus are the interconnect structures that are tightly arrayed within a probe apparatus. The interconnect structures are configured for a reliable electrical contacting during a high number of test cycles. With advancement of semiconductors, interconnect structures become increasingly smaller and tighter arrayed.
Interconnect structures need to meet several functional criteria. Firstly, they need to be sufficiently flexible and resilient to compensate for positioning discrepancies of test terminals. Secondly, the interconnect structures needs to scratch along the terminal's surface to remove any eventual insulating oxides and films prior to establishing a conductive contact to the test terminals. This scratching also known in the art as scribing is accomplished by endowing the interconnect structure with an elastic deformation characteristic that results in a relative motion of the interconnect's end along the test terminal's surface during an initial positioning. Thirdly, the interconnect structures must be simple in shape and configuration to be cost effectively fabricated in high numbers. Fourthly, the interconnect structures need to be configured for a cost effective assembly in ever increasing numbers and tighter spacing.
In the prior art, two main designs for interconnect structures have been implemented to address the needs stated above. According to a first design interconnect structures are fabricated as well-known buckling beams made of wire having a round and/or rectangular cross section. Buckling beams are oriented in a certain manner with respect to the tested terminals such that they buckle upon initial contact with the test terminals. The resilient buckling of the beams provides for suspension and scribing. Unfortunately, the buckling beams need to be held at both ends with sufficient lateral space to permit buckling in the middle of the buckling beams. This results in a relative complicate and cost intensive assembly.
In a second design concept, the interconnect structures are fabricated as spring like features directly on a face of a larger structure of the probe apparatus with which they are rigidly connected. Such larger structure may include a well-known space transformer and/or a well-known printed circuit board [PCB] transformer. During the contacting with the test terminal, the resilient deflection of the interconnect structures is opposed by the larger structure on which the interconnect structures are fabricated and with which they are rigidly connected.
The advantage of the second design concept is that the interconnect structures need not be held on both ends as is required for the buckling beam probes. Unfortunately, the effort for fabricating spring like interconnect structures directly on the face of a larger structure is relatively high. This is, because for a required contact force between the interconnect structure and the test terminal, the spring type interconnect needs to have a structural strength that is significantly higher than that of a buckling beam. Also, since the deflection of each spring like structure is opposed by the larger structure, each interface between the two of them may be exposed to high stresses. As a result, the interface may need additional structural support. In the prior art, complicated fabrication steps are performed for fabricating spring like interconnect structures. Such fabrication steps include multiple layer depositions and multiple layer shaping operations.
In the prior art, several problems associated with the fabrication of small scale interconnect structures directly on the face of a larger structure remain unresolved. One problem is to position and transport the miniature structure during its fabrication. A second problem is to precisely position an eventually pre-fabricated structure in its final assembly position on a larger structure. A third problem is to attach the eventually pre-fabricated structure in its final assembly position. The attachment is particularly problematic, where stresses are at a maximum in the attachment interface. The present invention addresses these problems.